Comparative estimation of a random error component of automatic well level gauges based on processing measurements of earth-tidal level of groundwater

Abstract

Relevance. Introduction of autonomous digital level gauges allows significantly expanding the range of tasks solved in various fields of geology and ecology, by increasing the frequency of measurements and applying mathematical processing methods to avoid distortions of different nature. The expansion of the field of application of downhole level meters makes it a topical issue to choose a particular type of device to ensure the required measurement accuracy. Aim. To consider the approaches to comparative estimation of random error of several types of automatic level gauges based on their recording of earth-tidal variations of groundwater level. Methods. Methods of compensating the influence of variations in atmospheric pressure on groundwater levels; methods of calculating tidal level variations; methods of correlation and frequency analysis of the calculated and experimental data. Results. The authors have carried out a comparative assessment of the accuracy in readings of several digital level gauges, installed in one well, by comparing the measured values of earth-tidal variations of the groundwater level with the calculated ones. Based on the experimental data, tidal variations of the groundwater level were obtained by eliminating distortions from variations in atmospheric pressure and then filtering with the moving mean. From correlation and amplitude-frequency analysis of the calculated and experimental data, indicators were determined for making a comparative assessment of a random component of the error of the tested level gauges. Conclusions. The approach suggested allows choosing independent digital level gauges with a minimum random error component using the totality of calculated parameters. The most promising way to eliminate the distorting effects of tidal variation of groundwater level is the method based on the cutter frequency filtering of the level signal measured by the level gauge.